Electric impedance tomography (EIT) is a noninvasive method, which is known per se, in which an alternating current of a few mA with a frequency of, e.g., 50 kHz is fed into an electrically conductive body, especially the human body, and the resulting surface potentials are measured at different points of the body. Based on mathematical reconstruction algorithms, which are known per se, a two-dimensional tomogram of the electric impedance distribution can be determined in the body being examined by the successive rotation of the current feed points around the body while measuring the surface potentials at the same time along a section plane. Such a tomogram of the impedance distribution of the human body is of interest in medicine, because the electric impedance changes both with the air content and with the extracellular fluid content in the tissue. Both the ventilation of the lungs and the shifts in the blood and serum due to physiological changes can thus be displayed in a locally resolved manner and monitored.
A known measuring system for electric impedance tomography is described in EP 1 000 580 A1, in which the graphic display of the measured impedance values is superimposed by the display of an imaging system for the same body slice in order to make possible a more accurate evaluation of the measurements performed by means of electric impedance tomography.